Species

potassium hydrogen antiporters

Summary

Summary: Membrane proteins that allow the exchange of hydrogen ions for potassium ions across the cellular membrane. The action of these antiporters influences intracellular pH and potassium ion homeostasis.

..8 to 7.6, at which point K+ extrusion ceased. The results suggest that K+ extrusion is due to an ATP-driven transport system that expels K+ by exchange for H+ and is active only at alkaline cytoplasmic pH...

..Our study reveals a novel functional role of K(+) in the binding of copper to apoFet3p and identifies a K(+)/H(+) exchanger at the secretory pathway as a new molecular factor associated with iron uptake in yeast. ..

..chx23 mutants displayed a high sensitivity to NaCl. Together, these data indicate that CHX23 is a probable chloroplast Na(+)(K(+))/H(+) exchanger important for pH homeostasis and chloroplast development and function. ..

..These results indicated the importance of Na+ in acidification of the cell interior via a Na+/H+ antiporter in order to support cell growth at alkaline pH(out) under conditions where the activity of a K+/H+ antiporter is marginal. ..

..In this defined medium, E. hirae did not grow well at pH near 9, but grew normally at pH below 7.5. This antiport system is important at high pH but dispensable at lower pH for ion homeostasis of this bacterium. ..

..Our results support the hypothesis of a functionally coupled transport system in the apical membrane consisting of a bafilomycin-sensitive V-ATPase and a K(+)-dependent, amiloride-sensitive K+/H+ exchange system. ..

..The H+ efflux rate was a hyperbolic function of K+ and increased with increasing extravesicular pH (pH(out)) from 7.5 to 8.5. These findings were consistent with the presence of K+/H+ antiport activity in these membrane vesicles. ..

..Inhibition of KefB activity by the addition of 10 mM potassium to the growth medium stimulates methylglyoxal-induced cell death. This establishes an essential physiological function for the KefB system. ..

..Thus, both CG10806 and CG31052 are functionally members of the CPA2 gene family, colocalise to the same apical membrane as the plasma membrane V-ATPase and show distinct ion specificities, as expected for the Wieczorek exchanger. ..

..A slower-growing E. coli strain was also found to accumulate RpoS and had enhanced resistance to NEM. These data emphasize the multiplicity of pathways involved in protecting E. coli cells against NEM. ..

..7 microM to 2.0 microM. The response was diminished in high K(+)-containing media, suggesting an effect of Nigericin as K+ transporter. This constitutes a novel piece of evidence for the important role of ions in SM metabolism. ..

..The difference is in concordance with the known ability of the mandibular gland of the rat, but not the rabbit or the mouse, to secrete a HCO3(-)-rich final saliva. ..

Maclean M, Ness L, Ferguson G, Booth I. The role of glyoxalase I in the detoxification of methylglyoxal and in the activation of the KefB K+ efflux system in Escherichia coli. Mol Microbiol. 1998;27:563-71 pubmed

..These data suggest that the glutathione-dependent glyoxalase I is the dominant detoxification pathway for MG in E. coli and that the product of glyoxalase I activity, S-lactoylglutathione, is the activator of KefB and KefC. ..

..It remains still unclear to what extent the K+(Na+)/H+ exchanger is inhibited by the different substances used. However, the ground state membrane permeability for K+ is much smaller than assumed so far. ..

..Alterations in the pHi do not accelerate the rate of detoxification of methylglyoxal. The mechanism by which methylglyoxal causes cell death and the implications for pHi-mediated resistance to methylglyoxal are discussed. ..

..Except for cells treated with ethidium bromide, no appreciable cell disruption was observed. The potassium efflux observed appears to be a membrane phenomenon reversible after washing with magnesium chloride. ..

..Evidence for several different regulatory effects emerged from studies of lacZ expression from the transposon of JC111 and from a tetA(L)-lacZ translational fusion introduced into the amyE locus of wild-type and JC112 strains. ..

..In summary care must be taken when using the putative K+/H+ ionophore nigericin as an experimental tool in synaptosomes, as under standard conditions (i.e. in the presence of high external Na+) nigericin behaves as a Na+/H+ ionophore. ..

..The model supports a hypothesis about participation of H(+)-ATPase in AP generation. ..

Ferguson G, Battista J, Lee A, Booth I. Protection of the DNA during the exposure of Escherichia coli cells to a toxic metabolite: the role of the KefB and KefC potassium channels. Mol Microbiol. 2000;35:113-22 pubmed

..coli cells to methylglyoxal results in DNA degradation, our results suggest this event is not essential for methylglyoxal-induced death. The implications of these findings will be discussed. ..

..These results suggest that the pHin-responsive primary K+/H+ antiport system (Y. Kakinuma, and K. Igarashi, J. Biol. Chem. 263:14166-14170, 1988) works for the pHin regulation of this organism growing at a high pH. ..

..The recent observations that Tet(L), a tetracycline-efflux transporter, and MdfA, a multidrug-efflux transporter, both confer alkali tolerance offer a striking case study in support of this hypothesis. ..